Rename package to com.doormile.miler, bump to 1.2.30+146

Play rejected the upload: the listing expects com.doormile.miler and the build
carried com.doormile.partner. This is a new app rather than an update — a
package rename gives Play a different app, so nothing carries over from the old
listing and versionCode restarts against an empty history.

applicationId moves; `namespace` and the Kotlin `package com.doormile.partner`
declarations deliberately do not. Those are the code's own package and are
allowed to differ from the application id — renaming them would mean moving
source directories to change a string nothing outside the build reads.

Four things did have to follow the id, because each of them names the app to
something outside it:

  * the SHIFT_END_ALARM broadcast action, or two builds installed side by side
    would answer each other's shift alarms;
  * the update checker's androidId in main.dart and UpdateScreen.dart, which
    looks the app up ON PLAY — left stale it would poll a different listing and
    report a rider up to date when he is not;
  * the Play URL the update screen sends him to, which would have opened the
    store page for an app he does not have;
  * the map tile and routing user-agents, which identify this app to OSM and
    OSRM.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EqVJPB9B4QuieZnBAAKgYQ

ABOUT_MILER.md

@@ -3,7 +3,7 @@
 The Doormile Miler app. One Android/iOS build that a rider signs into, gets his
 work for the day, and reports it back from the doorstep.
 
-`com.doormile.partner` · Flutter · GetX for the controllers that need it ·
+`com.doormile.miler` · Flutter · GetX for the controllers that need it ·
 one backend at `https://api.doormile.com/api/v1`
 
 This is the only document in the repository. It covers what the app is, how the